1. Field of the Invention
The present invention relates to an organic light emitting diode (OLED) display device, and, more particularly, to an OLED display device and a method for driving the same, which are capable of minimizing required memory capacity and the use rate thereof while achieving an enhancement in display quality through execution of overdriving (or accelerated driving) in accordance with image information of plural accumulated frames.
2. Discussion of the Related Art
Among flat panel display devices, which are presently an area of great interest, there are a liquid crystal display (LCD) device, a field emission display (FED) device, a plasma display panel (PDP) device, an organic light emitting diode (OLED) display device, etc. Among such flat panel display devices, the OLED display device is usefully applied to mobile communication appliances such as smartphones or tablet computers because it exhibits high brightness, and employs a low drive voltage while having an ultra-slim structure.
Such an OLED display device includes a plurality of pixels. Each pixel includes an OLED pixel including an anode, a cathode, an organic light emitting layer formed between the anode and the cathode, and a pixel circuit for independently driving the OLED pixel. The OLED display device also includes a driving control circuit for driving respective pixel circuits of the pixels.
In the OLED display device, a predetermined reference gamma voltage is sub-divided into gamma voltages for different grayscales. Using the sub-divided gamma voltages for different grayscales, digital data is converted into analog data signals (current or voltage signals). The analog data signals are supplied to respective pixel circuits, to enable an image to be displayed through the OLED pixels.
In order to reduce pixel response time, some conventional OLED display devices or LCD devices employ an overdriving (or accelerated driving) method in which image data is displayed in a modulated state. In the conventionally-employed overdriving method, image data of a current frame and image data of a previous frame are compared with each other, to set a degree of overdriving in accordance with an image data difference between frames and the set overdriving degree is then applied.
In such OLED display devices, however, it is necessary to set a degree of overdriving and to apply the set overdriving degree, taking into consideration image data of several previous frames, because the OLED display device has response characteristics influenced by accumulated image data, unlike LCD devices. Since the OLED display device is influenced by image data of several accumulated frames, degradation of picture quality such as over-shoot or under-shoot due to excessive or insufficient overdriving degree when the degree of overdriving is set and applied in accordance with image data of a most recent frame, may be encountered
To this end, in the OLED display device, a degree of overdriving must be set and the set overdriving degree must be applied, taking into consideration image data of several previously accumulated frames. However, excessively large memory capacity and excessively-increased memory use rate are required in order to store image data accumulated for several frames. For this reason, in applying the overdriving method to the OLED display device, many hardware problems must be taken into consideration.